We present an open source web application and ecosystem services model, People in Ecosystems/Watershed Integration (PEWI). PEWI integrates ecological models within an intuitive interface, allowing users to rapidly and dynamically evaluate how changes to agricultural land cover, use, and management affect ecosystem service outcomes. Users create and evaluate land-use and management scenarios in a virtual watershed across years and variable weather conditions using spatially explicit environmental patterns and dynamic feedback on 16 ecosystem service indicators. Indicators include agricultural production (i.e., crop and livestock) and environmental outcomes (i.e., water quality, habitat provision for biodiversity, soil quality, and carbon management). We based initial indicator equations on literature review, empirical data, existing models, and expert consultation, and finalized equations using a combination of testing, sensitivity analysis, and expert review. Model results allow users to explore nuanced tradeoffs and co-benefits between types and levels of agricultural products and other ecosystem services generated in a watershed. PEWI's niche as an ecological model is as a tool for engaging broad public audiences in understanding the science and management of landscapes and watersheds.